didn't. Such forms are used very frequently in informal English. Do-support is required for negated imperatives even when the verb is the copula be: Do not do that. Don't be silly. However, there is no do-support with non-finite, as they are negated by a preceding not: It would be a crime not to help him (the infinitive to help is negated) Not knowing what else to do, I stood my ground (the present participle knowing is negated) Not eating vegetables can harm your health (the gerund eating is negated) With subjunctive verb forms, as a present subjunctive, do is infrequently used for negation, which is frequently considered ambiguous or incorrect because it resembles the indicative. The usual method to negate the present subjunctive is to precede the verb with a not, especially if the verb is be (as do-support with it, whether it be indicative or subjunctive, is ungrammatical): I suggest that he not receive any more funding (the present subjunctive receive is negated) It is important that he not be there (the present subjunctive be is negated) As a past subjunctive, however, did is needed for negation (unless the verb is be, whose past subjunctive is were): I wish that he did not know it I wish that he were not here The negation in the examples negates the non-finite predicate. Compare the following competing formulations: I did not try to laugh. vs. I tried not to laugh. They do not want to go. vs. They want not to go. There are two predicates in each of the verb chains in the sentences. Do-support is needed when the higher of the two is negated; it is not needed to negate the lower nonfinite predicate. For negated questions, see the questions section above. For negated elliptical sentences, see the elliptical sentences section below. Negative inversion The same principles as for question formation apply to other clauses in which subject–auxiliary inversion is required, particularly after negative expressions and expressions involving only (negative inversion): Never did he run that fast again. (wrong: *Never he did run that fast again. *Never ran he that fast again.) Only here do I feel at home. (wrong: *Only here feel I at home.) Further uses In addition to providing do-support in questions and negated clauses as described above, the auxiliary verb do can also be used in clauses that do not require do-support. In such cases,